The V8 Owners Forum -

my v8's playing up

3.5 efi flapper

started as a misfire when hot

progressed to constant misfire 4 to 6 to 8 to 4 to 6 to 8 etc

then died

stripped the dizzy swapped the baseplate and amp and the coil strong spark from coil and ht leads while trying to sort it i filled the sump with fuel

so i swapped the oil and it started only on 6 first time never managed to drive it

then after i had let it run warm i noticed the expansion tank had mega pressurised but when i pulled the plugs they were dry

now it will idle on 6 or 7 i think but wont rev if i even tweak the throttle it dies out but if left the idle will rise and run on 8 for a seccond or 2 as the base idle is set high for my autobox but then drop back to a low idle and 6 cylinders

any ideas

btw its got a new coolant temp sensor and thermotime switch,

ive also been through a few ign amps before im using a 35dlm8 lucas dizzy

has always had a rough poppy idle but pulled very well

My first guess would be wiring on one side of the injectors? see wot anyone else chips in with !

have you changed the resistor pack for the injectors?
or even tried another injector driver relay (red relay in efi harness)

landybob_v8 wrote:started as a misfire when hot

progressed to constant misfire 4 to 6 to 8 to 4 to 6 to 8 etc

then died

stripped the dizzy swapped the baseplate and amp and the coil strong spark from coil and ht leads while trying to sort it i filled the sump with fuel

so i swapped the oil and it started only on 6 first time never managed to drive it

then after i had let it run warm i noticed the expansion tank had mega pressurised but when i pulled the plugs they were dry

now it will idle on 6 or 7 i think but wont rev if i even tweak the throttle it dies out but if left the idle will rise and run on 8 for a seccond or 2 as the base idle is set high for my autobox but then drop back to a low idle and 6 cylinders

any ideas

btw its got a new coolant temp sensor and thermotime switch,

ive also been through a few ign amps before im using a 35dlm8 lucas dizzy

has always had a rough poppy idle but pulled very well

Bob, Just thinkin' out loud here.

You have at least five separate problems.

1 Something in the system causing rough poppy idle. Sounds like its running lean. such as

#Pressure regulator stuck on 26 psi.
#Extra air valve stuck partially open.
#Air flow meter been tampered with giving excess flap spring pressure inducing a weak mix.

2 Something in the system caused the initial prob which progressed to a constant misfire such as

#Throttle pot noisy.
#Intermittant wiring fault around the injector resistors.
#Intermittant Efi earth


3 You now have an ignition problem due to stripping and reassembling dizzy and all its bits such as

#Incorrect ign timing
#Plug lead crossed
#Ign amp still faulty - or its wiring.

4 something mega-pressurising cooling system such as

#Blown head gasket
#Pressure release cap stuck closed.

5 Something caused an injector to stay open & fill sump with fuel such as

#Cold start injector stuck
#Thermotime switch (Still) faulty
#ECU output stage short circuit keeping four injectors open with fuel pressurised due to pump running constantly.

All the above reminds me when being lost in Dublin and asking a local for instructions the reply was - " If I were you sir, I wouldn't start from here!"

#You could try checking just the things mentioned above.
#You could try the methodical approach component by component.

You'll find some help you can download from here:

http://www.vintagemodelairplane.com/pag ... ech01.html

Bob, Just thinkin' out loud here.

You have at least five separate problems.

1 Something in the system causing rough poppy idle. Sounds like its running lean. such as

#Pressure regulator stuck on 26 psi. = dunno but it did it with a few of them swapped when ive looked for faults before come to think it could be due to my exhaust system and its high idle

#Extra air valve stuck partially open = when i cold start it starts fine but then the idle drops low until its warmed a bit

#Air flow meter been tampered with giving excess flap spring pressure inducing a weak mix. = any way to test?

2 Something in the system caused the initial prob which progressed to a constant misfire such as

#Throttle pot noisy. = dunno no spare to test either

#Intermittant wiring fault around the injector resistors. = fairly new loom

#Intermittant Efi earth = earth is bolted to the rear of the head and has good earth from the block to the chassis


3 You now have an ignition problem due to stripping and reassembling dizzy and all its bits such as

#Incorrect ign timing = my timing gun has died now so i cant check but when it was started shortly after being refitted it would run on 8 but then dropped to 6 then 4 then back to 6 and etc

#Plug lead crossed = definatly not 18436572 double cheked

#Ign amp still faulty - or its wiring. = could be ive done a new loom from the coil is there any way to test the amp?

4 something mega-pressurising cooling system such as

#Blown head gasket = all the plugs were dry though black and the coolant is free of oil and fuel but i have yet to do a sniff test

#Pressure release cap stuck closed. = dunno

5 Something caused an injector to stay open & fill sump with fuel such as

#Cold start injector stuck = not plugged in and hot day also

#Thermotime switch (Still) faulty = stuck my spare on to no avail

#ECU output stage short circuit keeping four injectors open with fuel pressurised due to pump running constantly. = dunno

when i cold started it it would rev and sound fairly normal but when idle and initial rev it would misfire

when left to get hot it would idle between 6 and 8 revving itself but would not rev and stall instead when the butterfly in the plenum was opened this is with the air filter removed also and just the air flow meter connected

ive just been outside it did fire but wouldnt kick in if i reved it it would stop firing with all the relays pulled to clear the fuel and another try same thing i could tell it still had a misfire by the sound of it firing mind

so now ive got a complete non runner on my hands

but on a plus note i just found a fiver on the stairs leading to the car park where the motor is that can go towards the mallory and webber carb now im going back to manual as well


any more ideas?

landybob_v8 wrote: any more ideas?

Yes, check out all the "Dunno's"

Such as you are able with the car not running, do the full range of analytical tests mentioned here:

http://www.vintagemodelairplane.com/pag ... djust.html

Learn how to test and adjust the Throttle Pot here:

http://www.vintagemodelairplane.com/pag ... Pot01.html

And how to test and adjust the Air Flow Meter here:

http://www.vintagemodelairplane.com/pag ... ter01.html

Regarding the fiver you found put it on the gee gee's at 500 to 1. If your luck holds you could get 2500 quid and replace your car - no problemo!

rightyho

since the rain eased off i managed to get it running

fitted a new baseplate and amp to the dizzy set the dizzy as per the land rover overhaul manual

that got it running 6 cyl on idle 8 on rev no pressurise to the cooling system

then it deteriorated to its normal 6 on idle 6 on rev didnt drop any more with good strong spark still

i noticed it pushed a shed load of water past the overflow on the expansion tank and it had seemed to have filled the sump, it seemed to run on fuel vapour for a good long time and i reckon i could still be sat there now cranking listening to it fire (full throttle mind)i had unplugged the relays from the efi system while trying to clear the cylinders

i changed the oil and it started still 6 idle 6 rev really low idle (its set high for my autobox) havnt checked the sump again but still chucked a load of water from the expansion tank, the coolant doesnt look oily and doesnt smell fuely either

the exhaust is chucking out blue smoke and proper stinks of fuel in the engine bay

ive done a compression test and its 125+ on all 8 cylinders with dry plugs though a light black coating on them

but i parked it up with quarter a tank of fuel when home after the fault since then it ran dry of fuel and i had to stick in 20 liters

been sat 3 weeks ish since fault showed and a lot of cranking

soon as the rain eases off im going to strip the engine down inlet manifolds and heads off to see what it looks like.

dont think it'll be head gaskets as it showed good on the comp test,
hopefully the block isnt cracked but hopefully ill find it.

landybob_v8 wrote:rightyho

since the rain eased off i managed to get it running

fitted a new baseplate and amp to the dizzy set the dizzy as per the land rover overhaul manual

that got it running 6 cyl on idle 8 on rev no pressurise to the cooling system

then it deteriorated to its normal 6 on idle 6 on rev didnt drop any more with good strong spark still

i noticed it pushed a shed load of water past the overflow

Could that just be loads of airlocks in the system causing it to boil?

on the expansion tank and it had seemed to have filled the sump, it seemed to run on fuel vapour for a good long time and i reckon i could still be sat there now cranking listening to it fire (full throttle mind)i had unplugged the relays from the efi system while trying to clear the cylinders

i changed the oil and it started still 6 idle 6 rev really low idle (its set high for my autobox) havnt checked the sump again but still chucked a load of water from the expansion tank, the coolant doesnt look oily and doesnt smell fuely either

If its not contaminated then the block and head gaskets are probably OK?

the exhaust is chucking out blue smoke and proper stinks of fuel in the engine bay

That could be rings not working properly or valve stem oil seals leaking and the smell of fuel in the exhaust might idicate a too rich mixture.

ive done a compression test and its 125+ on all 8 cylinders with dry plugs though a light black coating on them

That would also indicate running rich

Comments in red
Ramon

landybob_v8 wrote:but i parked it up with quarter a tank of fuel when home after the fault since then it ran dry of fuel and i had to stick in 20 liters

been sat 3 weeks ish since fault showed and a lot of cranking

Im not sure what this has to do with the fault condition unless the fuel has become contaminated with water???

Ramon

landybob_v8 wrote:soon as the rain eases off im going to strip the engine down inlet manifolds and heads off to see what it looks like.

dont think it'll be head gaskets as it showed good on the comp test,
hopefully the block isnt cracked but hopefully ill find it.

If the oil is not contaminated with water and the compression tests are ok what else makes you think it necessary to strip the heads off again.

The pressurizing of the cooling system might be due to lots of airlocks not being released so the coolant is boiling locally in the block and generating steam.

today i took the inlet manifold off and put the fuel lines on
i then pressurised the fuel rail with fuel by pushing the flapper in
nothing leaked past the injectors so they dont leak its still possible that there on for too long

thought as im this far i took the heads off anyway and found the bolts i had bought off ebay were far too easy to undo (i could have done it with a normal ratchet), though the pistons didnt seem steam cleaned.

that could have pressurised the cooling system as the compression could have leaked.

i did notice some pitting before i put the heads but it sat within the gasket though, when i took them back off i found a big scratch when i took them off that may have happened during fitting, that touched the pitting and went past the gasket that could have caused something

im replacing that head with one i know is good once its cleaned with new stem seals fitted to elimenate the head, ill decide on the other one once its removed tomorrow.

so far i havnt found anything obvious yet

and may stick my twin su carbs back on that i havnt touched since i striped one of my old engines that ran with no fault for years to see if it will run nice, then back to the efi to see (lucky i have a good stock of gaskets)

hopefully ill find it by tomorrow night

*note to self by some diagnostic type tools a working multimeter might help for a start

on another note when i dropped the oil yesterday it poured out like id stuck in a load of paint thinners and wasnt contaminated like it would be with water

definatly fuel this could have leaked past the rings who knows

Sounds like you're having fun Rob

I reckon what you need is these heads I've got sitting in my shed. I could do with those 3.5's you've got down there too.